1. Field of the Invention
The subject of the present invention is a process for the preparation of carboxylic acid chlorides of the benzene series by the reaction of the corresponding carboxylic acid esters with trichloromethylbenzenes in the presence of a catalyst.
2. Discussion of the Prior Art
It is known to prepare aromatic carboxylic acid chlorides from the corresponding carboxylic acid alkyl esters and trichloromethylbenzenes, using Lewis or Bronsted acids as catalysts, preferably the chlorides of zinc, aluminum, iron or sulfuric acid (cf. French Pat. No. 820,698 and German "Offenlegungsschrift" No. 1,954,793). Iron and aluminum are used as catalysts also in the preparation of aromatic carboxylic acid chlorides in which polyesters of aromatic carboxylic acids are reacted with trichloromethylbenzenes (German Offenlegungsschrift No. 2,311,825). It is important in all of the above-named processes that the competing Friedel-Crafts reaction be prevented insofar as possible.
The use of the above-named catalysts has several disadvantages: The reaction takes a very long time, and in some cases additional catalyst must be fed in constantly. The reaction times are long and the volume-time yields are, accordingly, low.
The problem has therefore existed of devising a process for the preparation of the above-named carboxylic acid chlorides which will result in higher yields of the desired carboxylic acid chloride with shorter reaction times and, insofar as possible, low temperatures.